Code P0102 Mercedes C180 W203

Mercedes C180 W203My car has been acting weird recently. It idles roughly (sometimes violently), consumes loads of fuel and at times accelerates sluggishly. The engine light comes on with Code P0102 (air flow circuit too small) and Code P0172 (Mix bank 1 rich).

What should be me course of action to remedy the problems?

Appreciate your assistance!



Before replacing the mass air flow sensor, try replacing the air filter and cleaning the air flow sensor with low compress air or mass air flow sensor cleaner. Reset code and drive vehicle. If the code comes back, it may be necessary to replaced the mass air flow sensor.
The Code P0102 is set when an excessively low voltage from the sensor is sent to Engine Control Module (ECM).

Mercedes-Benz Code P0102  – Mass or Volume Air Flow Circuit Low Input

The Mass Air Flow (MAF) sensor is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the Engine Control Module (ECM).

Temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. More air, the greater the heat loss. Therefore, the ECM must supply more electric current to maintain the temperature of the hot film as air flow increases. The ECM detects the air flow by means of this current change.

Code P0102 Possible symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)
  • The Engine stalls
  • Engine running rough
  • Excessive fuel consumption
  • Excessive smoke

Code P0102 Possible causes

  • Faulty mass air flow sensor
  • Intake air leaks
  • Dirty mass air flow sensor
  • Dirty mass air filter
  • Mass air flow sensor harness is open or shorted
  • Mass air flow sensor circuit poor electrical connection

Mercedes Benz CodeP0172 – System Too Rich Bank 1

With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.

In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the MIL (2 trip detection logic).

Code P0172 Possible causes

  • Faulty front heated oxygen sensor
  • Ignition misfiring
  • Faulty fuel injectors
  • Exhaust gas leaks
  • Incorrect fuel pressure
  • Faulty Mass Air Flow (MAF) sensor